Before you read my FAQ below, check out the following link for a helpful overview of PERCS: https://www.stlouischildrens.org/conditions-treatments/center-for-cerebral-palsy-spasticity/tendon-lengthening-following-sdr


What is PERCS? How is it different from SPML? How is it different from traditional lengthening?

Part of the confusion between PERCS and SPML is that people often use the acronym “PERCS” when they mean “SPML.” Both procedures are percutaneous lengthenings in the sense that they involve relatively shallow incisions through the skin. But Dr. Dobbs’ PERCS procedure at St. Louis Children’s and the SPML procedure developed by Dr. Nuzzo are two different types of surgeries.

According to my understanding, PERCS and SPML are both minimally invasive tendon lengthening procedures. PERCS involves tiny incisions made through the skin with a scalpel. SPML involves tiny incisions too, but they’re like little pinprick holes made with tools that are similar to those used in eye surgery.

SPML (Selective Percutaneous Myofascial Lengthening) is performed at the junction where the tendon and the muscle meet. As the name suggests, the myofascia (the fibers that surround the muscles) are lengthened in SPML. Dr. Dobbs’ PERCS typically involves lengthening the tendon itself, via small nicks along the tendon like the slits in a feather. My understanding is that Dr. Dobbs also addresses fascia, though, depending on the type of PERCS. Dr. Dobbs’ gastroc PERCS, for example, involves only releasing the sheath over the gastroc muscle, and sometimes he also releases fascia in hamstring PERCS, in addition to feathering the hamstring tendon(s).

Dr. Park and Dr. Dobbs at St. Louis Children’s Hospital much prefer PERCS over SPML, so most patients who need tendon surgery after SDR pursue PERCS.

Traditional lengthening surgeries often involve cutting through a tendon and reattaching it, which requires larger incisions and creates more weakness compared to the minimally invasive PERCS, where the tendon is mainly just feathered. That feathering allows the tendon to stretch more, much like slits along the length of a rope would allow the rope to stretch farther. If you are an adult who had lengthening surgeries as a child, you likely had the traditional version.

Why do some people need this follow-up surgery?

There are two different kinds of muscle tightness: tightness due to spasticity and tightness due to a shortened tendon.

Spasticity occurs when there’s a disruption of the messages traveling between the brain and spinal cord. A spastic muscle tightens up more as it’s moved quickly. This is the type of tightness that is directly addressed through SDR.

The other kind of tightness is due to tendons that have become too short, often as a result of long-term spasticity, lack of stretching, or growth spurts.

(Note: “Lack of stretching” doesn’t necessarily mean that someone is skipping their stretching routine. People with CP tend to develop tighter muscles also as a result of their gait patterns being different; these gait patterns don’t always allow the muscle to stretch all the way. For example, a child who walks with their heels down and knees straight is getting the opportunity to stretch their heelcords and hamstrings every time they take a step. If a child with CP is walking on their toes or crouching as they walk, they aren’t naturally stretching their muscles through the full range of motion, and this can lead to tightness over time.) 

Tendon shortening that is mild or in very young children can often be addressed by stretching. However, over time, the cellular structure of the tendon actually changes so that the tendon isn’t as elastic as it once was. When this happens, we say that the tendon has a contracture, or permanent muscle tightness. Contractures can’t be addressed by stretching alone; the tendon needs to be surgically lengthened.  

What are the benefits of PERCS?

For many people, PERCS is the “icing on the cake”! The benefits will differ for everybody depending on their situation and the type of PERCS they had, but it helped me a lot. In the months after SDR but before PERCS, I developed low-back pain not directly related to SDR, but because my hamstrings were becoming stronger without spasticity but were still tight from contracture, they were pulling hard on my back. Also, while SDR greatly improved my ability to stand straight, I still couldn’t extend my knees all the way, especially on my right (more affected) side. Hamstring PERCS gave me that range I was missing so that I could fully straighten my knees, and I woke up in the recovery room with my back pain gone! It also helped resolve some knee pain I had been experiencing after hamstring stretching.

Many people report that PERCS helps them gain motor skills, improves their pain, and helps with their gait and posture.

Are there any drawbacks to PERCS?

Yes. Some people report some long-term weakness afterward that can be difficult to address—especially adults, based on what I’ve heard. This has been my experience too: Even past a year post-op, I still didn’t quite have the strength in my hamstrings that I did before surgery. This is a common trade-off for lengthening surgeries, as every time a tendon is cut, it’ll get a little weaker, so Dr. Dobbs and Dr. Park recommend adult PERCS with caution. For some adult PERCS patients I’ve spoken to, post-op weakness has been really difficult for them. Many are still happy they had PERCS, but some of them do regret their lengthenings because of the ongoing weakness they experience. (My understanding is that children, in contrast, generally bounce back faster after PERCS.) Again, all surgery has risks, so you need to weigh the pros and cons with your surgeon(s) and the rest of your care team.

For me, the weakness I’ve noticed is slight—it doesn’t impact me functionally, and it may just take more time for that strength to rebuild. I’ve only noticed when doing certain exercises that isolate my hamstrings, and it may also be due to the new range that I’ve gained after surgery. I’ve been told that when a tendon is lengthened to a range it hasn’t been able to access before, it’ll be particularly weak in that new range. 

Your care team and surgeons can help you decide which treatment options are best for you. For me, PERCS has still been completely worth it; I’m even more comfortable than I was after SDR, my range of motion is so much better, and my pain is much improved.

How will I know if I need PERCS after SDR?

If you apply for SDR in St. Louis, you’ll often be told in your acceptance letter (if you’re international) or phone call (if you’re in the USA) if they think PERCS will be necessary. Sometimes they won’t know for sure until they evaluate you in person. Sometimes they need to wait until after your SDR so they can see how tight you are after your spasticity is gone—it’s not always easy to tell the difference between tendon tightness and spasticity. Sometimes they’ll want to re-evaluate you for PERCS 4 months after SDR, 6 months, a year, or longer to see if you can stretch out the affected muscle group on your own. And sometimes people develop tightness in the years after SDR, meaning that they need PERCS several years post-SDR even if they didn’t need it at first. This is especially true in growing children, who may become tighter during growth spurts. 

If you think you might need PERCS after SDR and you’re pursuing SDR in St. Louis, it’s a good idea to talk to the team beforehand about scheduling an appointment with the orthopedic surgeon, Dr. Dobbs. Sometimes he comes to evaluate people in the hospital right after SDR; patients who live in the USA often schedule an appointment with him during their mandatory 4-month followup. 

If I do need PERCS, how long after SDR will I have it?

It varies a lot depending on the situation. Many international patients have PERCS a week and a half to 2 weeks after SDR. Patients who live in the USA often have PERCS at their 4-month followup, but they may have it as early as 2 months post-SDR if the team judges that their contractures are severely interfering with their progress. Adults are often recommended to wait until a year after SDR so that they can build up strength before undergoing another surgery, although this schedule is often somewhat negotiable depending on your life obligations. I had PERCS at 9 months post-SDR, as I had a trip I needed to go on at 1 year post-SDR. 

Do other hospitals perform PERCS?

Yes; my local surgeon actually offered to perform it for me, although he said that he hadn’t done many percutaneous lengthenings. I have great respect for my local surgeon, but I opted to go to Dr. Dobbs because of his level of experience and expertise with this procedure. As always, do your research carefully, and be careful not to confuse feathering lengthening procedures with SPML (which surgeons often refer to as PERCS as well, even though it’s a different procedure; see first question). 

Is it painful?

Yes, but it’s not as big of a surgery as SDR, so you typically won’t need heavy-duty pain meds. Everyone’s experience is different, but I personally found PERCS to be less painful than SDR, and the hospital stay was much easier. I woke up in the recovery room with my pain at about a 3. Bumps on the floor hurt, like when they were moving my hospital bed to my room, and I did have some muscle spasms that hurt quite a bit, but these gradually went away over the course of 2 weeks. By 2 weeks post-op, I had no more PERCS-related pain. 

I had hamstring PERCS on both legs, which required a scar on the outside and inside of each knee (most people who get hamstring PERCS only need an incision on the inner knee, but adults often need both, as do children with more severe tightness). The pain was like a ripping, burning sensation in my upper calf when weightbearing for the first week or so (I know, “ripping” sounds unpleasant, and it was painful, but it’s not as bad as it sounds; the tendon isn’t actually ripping.). When sitting or lying down, I often had no pain at all. After a few days, I was completely off pain meds.

Your experience may differ depending on what kind of PERCS you need, whether you have one leg or both legs done, how severe your contractures are (PERCS is done “à la carte”—the tendon can be feathered just a little, or it can be feathered a lot, depending on your needs), and how many muscle groups are lengthened. Children, especially, often seem to find the immediate PERCS recovery to be more painful than SDR, but children tend to experience less pain after SDR compared to adults—so it’s all relative.

Should I bring my wheelchair for PERCS?

Yes, I’d strongly recommend it! I walked independently before PERCS, but it was hard for me to bear weight on my legs for the first couple weeks after surgery. It was a different kind of weakness than after SDR; after SDR, my legs didn’t hurt—they just felt like jelly. After PERCS, I didn’t have jelly legs, but it felt like I had a bad muscle pull, and I sometimes had unpredictable muscle spasms at first, which would cause me to start to fall. Our hotel (The Chase) had a shuttle that had a step to get inside, and while I managed this step with heavy support after SDR, my legs refused to let me generate the power I needed to step up the afternoon after PERCS. It was earlier on in my recovery (day 5 after SDR vs. day 1 after PERCS) so it’s perhaps not the fairest comparison, but my mom ended up pushing me back to our hotel in my chair. I also needed the chair to navigate the airport, although I could stand and take a few steps by then (day 4). 

Will I need a cast after PERCS?

It depends on the type of PERCS you have. Common PERCS are on the heelcords (Achilles tendon), gastrocs (calf muscle), hamstrings, or adductors (inner thigh). 

If you have heelcord PERCS, you will wake up from surgery with a below-the-knee cast. The casts will stay on for 10 days (if you’re international) or 4 weeks (if you’re from the US), and then you’ll have to wear AFOs (below-the-knee braces) for about 6 to 8 weeks, followed by just the shorter brace (SMO) for another 6 to 8 weeks. You’ll also have night splints to wear at night for a while. 

If you have gastrocs PERCS, you won’t have cast, but you’ll follow the same schedule as above (6 to 8 weeks with the AFO, followed by 6 to 8 weeks with the SMO). 

If you have hamstring PERCS, you’ll wear soft knee immobilizers while you sleep for the first 6 to 8 weeks after surgery.

These timelines may vary according to your individual situation, so as always, check with your surgeon and PT. 

How long can I expect to be in the hospital after PERCS?

Usually, people stay 1 night, and they’re on the 6th floor (general surgery) instead of the 12th floor. That overnight stay is mainly for them to administer a round of IV antibiotics and to make sure that your pain is well-managed. The next morning, a PT comes to your room to help you out of bed so you can take some steps, usually with a walker. I thought it was a much easier stay than the SDR stay. 

How long should I stay in St. Louis after PERCS?

Dr. Dobbs’ nurse recommended to me that I plan to stay at least an extra night in the hotel after being discharged from the hospital. You can go home the same day as discharge, and many people do, but if you can afford to stay at least one extra night, I’d recommend it. It’s just helpful to get some time to rest and recharge before traveling. I was discharged on a Wednesday and stayed until Saturday morning, which was nice. I booked a couple PT sessions (mine were covered by my insurance) to get some ideas for post-op rehab, slept a lot in my hotel, practiced some walking, and did a little bit of light exploring of St. Louis (we went to the zoo; I took my wheelchair). 

What was your recovery like?

I found the initial recovery to be easier than SDR, although that’s not the case for everyone (some find it harder). I liked that I could get out of bed the very next day, and while I needed assistance to walk for the first couple weeks, by 2 weeks post-op I had no pain and was back to walking independently. (Again: Your experience may vary; many people take longer, particularly those with more involved CP and older adults.)

The first week and a half was difficult for me; I had a lot of muscle spasms and some bruising, and it was tough to feel like my legs weren’t cooperating with me. But by 3.5 weeks, I went rock climbing for the first time in my life, and at 2 months post-op, I went on my first-ever solo plane trip to visit some friends. My endurance was definitely affected during that trip, and at that point, I was still working to regain some skills I had developed after SDR (e.g., navigating curbs), but my friends gave me a hand when needed.  

Long-term, I felt that the recovery was a bit harder in some ways, just because I had to work so hard to regain lost strength (and maybe I still haven’t gained it all back yet, even 2+ years post-op). The recovery process depends on lots of factors (e.g., age, pre-op abilities, severity of contractures, co-existing orthopedic issues, rehab, type of PERCS). 

What kind of rehab should I do?

The St. Louis protocol is 4 to 5 PT sessions per week for 6 months to a year, followed by a gradual reduction, but your rehab schedule may depend on your individual situation; talk to your care team to figure out what’s best for you. As for the type of exercises, I did a lot of practicing walking while trying to consciously activate my new range of motion. Treadmill walking is particularly helpful for that. I also did a bunch of targeted hamstring exercises! Once your bandage comes off (after 10 days) and the stitches have dissolved, swimming may be a great form of rehab too. Take a look at the Exercises page for more exercise ideas.